crater in rod bearing, what does this mean? Options

[mightyohm]

This is an extreme closup of a rod bearing on a 2.0 I tore down. There is a small crater in the bearing. It is at least a few thousands deep and definitely catches a nail. The scratches through it are from me scraping at it with my nail to see if more would flake off.

Anyone seen this before? I have a cam bearing that is much worse but no pics yet.

[Thorshammer]

Many of you have seen this before, but this is indeed corrosion. When the motor is stored for a long period of time, the oil should be changed prior to storage. Combustion contaminates when mixed with moisture can form acid concentrations. The surface (babbitt) of most bearings is very porous and is easily attacked or etched. The first time the motor turns over, it flakes off and this is what you get. Some aftermarket bearings don't use as porous a material as the factory bearings and it will happen much less. But keep in mind when you rebuild a 914 motor you don't normally plan on storing it for long periods of time. The bearing porosity is also a good reason to "presoak" rod and main bearings in oil warmed to about 140 degrees and then allow them to cool. This does a much better job of bearing break in than assembly lube alone. Others may have a better way. Suggestions?.


Erik Madsen
Madsen Engineering